Subscriptions are always complicated. This plugin uses PayPal Express Checkout method for payment and uses shortcodes for managing the system.
All you have to do is insert the shortcodes in their rightful places, set up the paypal credentials in the setup page and you are ready to go.
You can find more things here: http://attilaordog.wordpress.com/2014/09/30/paypal-yearly-subscription/
